The goal of our research program is to critically investigate the influence of vitamin D on calcium and bone metabolism in the elderly. This will be accomplished by: 1) evaluating the vitamin D status of Blacks, Asians, Hispanics and Caucasians of lower economic means in a less defined environment, in comparison with residents at the Hebrew Rehab Center of the aged (HRCA), 2) studying the vitamin D daily requirement for the elderly, 3) determining whether vitamin D supplementation will protect bone mineral density of the elderly.